THE FUTURE OF THE SUBMARINE’S SEA DENIAL MISSION

The submarine’s redeeming virtue was its stealth, which let disadvantaged navies operate in waters dominated by an opponent stronger on the surface. For that reason the modern submarine began as a way for inferior forces to contest the naval supremacy of the dominant powers, be it the American TURTLE in the Revolutionary War, the Confederate HUNLEY in the Civil War or John Phillip Holland’s early experiments, subsidized by the Fenian Brotherhood.
In a more developed form it enabled the Germans to try to strangle British shipping in the world wars; the United States to do the same against Japan in the western Pacific and its home waters during World War II; and the Soviet Union to threaten the lifeline between the United States and Europe in the event the Cold War turned hot.
The Submarine’s capability to perform that mission has only continued growing since then. Air-independent propulsion systems give even diesel boats long endurance while submerged, and indeed, may let them lie quietly on the bottom in wait for surface ships to pass overhead as they play underwater sniper. At the same time developments like super cavitating torpedoes and the widening use of anti-ship and land-attack missiles aboard submarines increase their striking power.
That increased capability, however, seems unlikely to find its primary use in the anti-shipping mission. The major navies can accomplish the anti-shipping more effectively with other systems because of the capabilities of their air forces and surface fleets, and the weakness of their most likely opponents in the same areas. For that reason, they increasingly point to the sub’s usefulness in gathering intelligence, supporting special-operations forces and launching land-attack cruise missiles.

Of course, this is not necessarily the case with Third World navies, which today operate hundreds of submarines. Jobs like inserting special operations forces or launching land-attack cruise missiles can be done by systems other than submarines, and more cheaply. While richer navies like those of the United States or Britain can weigh the pros and cons of using subs in these roles, countries with more limited means, and a more regional orientation, are bound to find such approaches not worth the cost. At the same time they can not count on air and surface power to fulfill the sea denial mission the way the United States and its major allies can. This means that the future of the submarine as an instrument of sea denial will be most evident in the uses to which smaller and poorer navies put them.
Third World Submarine Forces and the Sea Denial Mission
Third World navies are typically outfitted to fight comparable opponents, which may suggest that their situations will resemble smaller-scale versions of the major twentieth century conflicts. This line of thinking certainly has some validity. To find a real-world analog to the mechanized, naval and air battles of the world wars, historians generally look to conflicts like the Arab-Israeli Wars (especially 1967 and 1973), the lndo-Pakistani Wars (particularly 1965 and 1971), the Iran-Iraq War (1980-1988) and recent wars in sub-Saharan Africa (like Ethiopia-Eritrea).
Futurists, equally, point to such scenarios when looking for the next conventional war. Where large-scale submarine action aimed at denying an enemy the seas is concerned, a conflict in the Straight of Formosa, with China attempting to use its submarine force in a blockade against Taiwan, is perhaps the most likely one. Even under the most optimal circumstances (the commitment of every operational sub to the theater, the use by every submarine of its entire payload, etc.), however, China’s Submarine Force can impose only limited costs on Taiwan, well below what would be required to force its capitulation.2 China’s Submarine Force is modernizing, but likely to shrink in size as it sloughs off its large number of obsolete Romeo-class vessels, and replaces them with fewer, costlier vessels of the Kilo and other classes. As a result, the balance of power between China and Taiwan is unlikely to change dramatically in the foreseeable future because of any planned changes to China’s Submarine Force.
At the same time, it is difficult to picture any other, comparable contest turning out differently. North Korea, for instance, has some two dozen submarines, and could conceivably use them to blockade South Korean ports, but its obsolescent (and perhaps largely unserviceable) force would have virtually no chance of success, even without American intervention. Iran’s three Kilo-class submarines would accomplish less than that in an attempt to block the Strait of Hormuz, even allowing for the difficulty of anti-submarine operations in that area.
In short, the quality and quantity of Third World submarines is severely limited by their economic and technological disadvantages. Even a Kilo-class sub, at over $200 million a copy, to say nothing of lifelong operating costs, is far from being a cheap alternative. Keeping even one operational at any given time will mean buying at least two such boats. Moreover even nations like China and India have had difficulty constructing indigenous submarines of any type, with nuclear subs, which can carry a price tag in the billions, taxing their industrial capability to and beyond its limits.
As a result, virtually any sea denial strategy such a navy pursues would have to be highly asymmetrical. At its simplest, the fact is that the well-publicized sinking of even a single ship can have highly disruptive effects on the movement of shipping, and compel a diversion of naval assets that might have been used in other ways. Nonetheless, as the Tanker War of the 1980s demonstrated, such an approach can only go so far. Tanker traffic continued through the Persian Gulf despite a very large toll in damaged and sunken ships. The political backlash from an attempt to interfere with the freedom
of the seas can also be disastrous, as Germany found in World War I, and as also became a factor in the Iran-Iraq War.
Indeed small Submarine Forces might do best to ignore civilian targets and concentrate on naval ones. The successes of Germany’s small U-boat force at the start of World War Il, like the U-47’s sinking of the battleship ROY AL OAK, were generally of this kind. The most likely mission of the Soviet Union’s rather larger Cold War-era Submarine Force in the event of a conflict in Europe would, similarly, have been to cut off the flow of military reinforcements to the battle zone. They might, for instance, be dedicated to a carrierkiller mission, long a concern for American planners.

Alternatively, such submarine forces would have to play a supporting role to other, simultaneous approaches, rather than being in the lead as they were in Germany’s case in World War II, and the Soviet Union’s in the Cold War. A China, Iran or North Korea, as a practical matter, would have to depend more on other assets in any presently plausible situation.

Alternative Approaches
Navies large and small have a whole host of anti-shipping, sea denial options, in areas where an opposing navy controls the surface, that do not require submarines at all- in other words, to accomplish the submarine’s traditional mission without submarines. Four of these will be discussed here.
The first is the use of stealthy surface vessels and aircraft, other systems which capitalize on the sub’s defining trait. Of course, even small warships are large enough targets that they are very difficult to make stealthy. Nonetheless relatively small, perhaps semisubmerged warships, would offer some capability. The demonstrated capabilities of stealth aircraft speak for themselves (provided that their bases can be kept operating), and this technology is already beginning to proliferate. In its Medium Combat Aircraft even India aspires to an indigenously built stealth bomber.
The second possibility is a variant on one widely mentioned concern, namely the risk that terrorists, rogue states or other parties might use freighters as launchers for crude cruise missiles. Such ships could also be used as platforms for anti-ship missile launchers (or mine-laying), in the manner of armed merchant ships or Q vessels in earlier periods.
The third is a dependence on the use of long-range land-based missiles, cruise and ballistic, both against shipping, and against port facilities, possibly from concealed or buried launchers not easily identified by space surveillance, or immediately susceptible to air attack. Observers convinced of China’s ability to blockade Taiwan are more likely to point to the country’s massing of ballistic missiles on its side of the straits than it submarines as a potentially decisive factor.
Finally, they could use special-operations forces against an opponent’s harbors and naval bases, infiltrating them through routes other than a sub would take to do the same job. They might sink warships and civilian vessels in port, as well as attacking the shore facilities ships need to load and unload their cargo. Should they attempt to explode an oil tanker or liquefied natural gas carrier inside the port, the result could be equivalent to a massive air attack. While the main attention has been paid to the ability of terrorists to stage such attacks, a large, national special-operations force, such as North Korea’s, would be much more capable of such an ambitious operation.

Given this situation, in which Submarine Forces of the kind they can afford are inadequate to a serious sea denial mission even as other, cheaper weapons and tactics seem to hold real promise, it is not surprising that even smaller navies are looking to other missions for their subs. Israel, India and North Korea may be looking to use their subs as a sea-based nuclear deterrent by equipping them with cruise or ballistic missiles, as the five members of the United Nations’ Security Council have long done.

Conclusions
The submarine began its life as a weapon with which weak naval forces could fight stronger ones. Today, however, submarine advocates reasonably claim that the submarine is today’s capital ship. Possession of a militarily capable force of capital ships is now more than ever a mark of being a great power, at sea as in other areas, of being that stronger fleet, and the submarine’s traditional relevance may be declining accordingly.
While this has to some extent always been the case- the notable submarine users of the twentieth century all having been great industrial powers capable of deploying large numbers of boats- this is now the case even more than before. This is not to say, of course, that the use of subs in the anti-shipping role on the scale seen in the world wars is entirely out of the question. Rather, it is to say that this is something that only a large peer competitor such as Germany in the world wars or the Soviet Union in the Cold War can seriously attempt, even if only a regional level, and there is presently no such player. Many experts believe that in the future, China might combine both the means and the political will to do so, though only time will tell.
Apart from this, submarines are likely to find themselves increasingly used in niche, asymmetrical or supporting roles, in smaller and poorer navies as well as the wealthier ones finding themselves without traditional challengers. Even allowing for matters of prestige and bureaucratic politics, the attractiveness of the submarine in those roles will be critical in determining the degree to which navies large and small continue investing in them to the degree that they have in the past.